(~ 
c 
The! 
Function:  Factorial, Binomial  Q  0 
The! 
symbol 
is 
formed 
by overstriking 
the 
quotation 
mark ( , ) and 
the 
period (.). 
Monadic (One-Argument) Form:  Factorial  !B 
The 
factorial 
function 
result 
is 
the 
product 
of 
all 
the 
positive integers from 
one 
to 
the 
number 
value 
of 
the 
argument. 
The 
argument 
can 
be 
a positive numeric scalar, 
vector, 
or 
other 
array. 
The 
shape 
of 
the 
result 
is 
the 
same as 
that 
of 
the 
argument: 
p+ 
24-
:l.X2x3X4-
24-
!1 
2 
:~ 
4-
~'5 
l. 
,') 
.:.. 
6 
2
1
.1. 
120 
The 
factorial 
function 
also works with decimal numbers 
and 
zero, 
but 
negative 
integers are 
not 
allowed.  When used 
in 
this way, factorial can be defined by use 
of 
the 
mathematical gamma 
function 
- (!A) 
is 
equal 
to 
gamma (A-1): 
! 3 . 1 
'+ 
7.173~5 
!O 
1. 
If 
the 
argument 
is 
an array, 
the 
function 
is 
extended 
to 
each 
of 
the 
elements: 
B 
... 
2 
2pO 
1 
") 
..... 
:~ 
B 
() 
1. 
I'Jr 
.:.. 
3 
!B 
:I. 
:1. 
,') 
.. 
'-
6 
59